import tkinter as tk


window = tk.Tk()
window.title('my window')
window.geometry('200x200')


var = tk.StringVar()
l = tk.Label(window, bg='green', width=20, text='empty')
l.pack()


def print_selection():
    l.config(text='you have selected' + var.get())
    
r1 = tk.Radiobutton(window, text='Option A',
                    variable=var, value='A',
                   command=print_selection)
r1.pack()


r2 = tk.Radiobutton(window, text='Option B',
                    variable=var, value='B',
                    command=print_selection)
r2.pack()


r3 = tk.Radiobutton(window, text='Option C',
                    variable=var, value='C',
                    command=print_selection)
r3.pack()


window.mainloop()
